refactor(editor): get loading icon with theme (#12079)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - Introduced a unified loading spinner icon that adapts to light or dark themes automatically.

- **Refactor**
  - Streamlined loading icon usage across the app by replacing multiple theme-based icons with a single helper function for consistent and simplified icon management.

- **Chores**
  - Removed an unused dependency to improve package management.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

yarn.lock

@@ -2407,7 +2407,6 @@ __metadata:
   version: 0.0.0-use.local
   resolution: "@blocksuite/affine-block-attachment@workspace:blocksuite/affine/blocks/attachment"
   dependencies:
-    "@blocksuite/affine-block-embed": "workspace:*"
     "@blocksuite/affine-block-surface": "workspace:*"
     "@blocksuite/affine-components": "workspace:*"
     "@blocksuite/affine-ext-loader": "workspace:*"